Colour bleed?

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Joined: Jul 30 2011
Posts: 86

Hi,

I wonder if the composite video output on my Apple IIe (US origin) is too strong for my monitor?

A screen of text is displayed clearly and correctly but the problem lies when color graphics are produced. Blocks of colour show up ok but if there is ant text on the same screen (white letters) there is what I can only describe as random colur bleeding or smudging around the text.

Is this due to an excessive output signal and how can it be lowered or do I need to look at somthing else?

Cheers,

Richard.

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magnusfalkirk's picture
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Joined: Feb 18 2007
Posts: 268
Re: Colour bleed?

retroaudio wrote:

Hi,

I wonder if the composite video output on my Apple IIe (US origin) is too strong for my monitor?

A screen of text is displayed clearly and correctly but the problem lies when color graphics are produced. Blocks of colour show up ok but if there is ant text on the same screen (white letters) there is what I can only describe as random colur bleeding or smudging around the text.

Is this due to an excessive output signal and how can it be lowered or do I need to look at somthing else?

Cheers,

Richard.

Actually Richard that is just the standard Apple II color scheme. Whether Low-Res, Hi-Res or Double Hi-Res, if I remember right, text on the graphic screen has some color bleed to it. I can't explain why, I'm not at all techy, but maybe somebody else can.

Dean

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Think Different - Apple II Forever!

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Joined: Jun 18 2010
Posts: 107
Re: Colour bleed?

That's just the nature of composite video. When you are in text-only mode, the Apple shuts off the color burst portion of the composite signal so the monitor goes into monochrome mode, thinking it's just a black-and-white video source. This turns off the monitor's color processing circuits giving a much sharper image, free from color artifacts.

Any color graphics modes (including mixed text/graphics) turns the burst back on and the monitor correctly decodes the color image. Unfortunately, it also incorrectly decodes some the high frequency text edges as color info which gives it that bleeding or color edging effect. A monitor with a comb filter might do a better job of decoding the composite image.

gsmcten's picture
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Joined: Oct 4 2005
Posts: 2609
Re: Colour bleed?

"Color Killer"

Many moons ago (between '78 and '80), Woz was having that same problem with color bleed.
As I remember the story, he came up with the "Color Killer" hack and placed the procedure into one of the books that came out during that time period.
I have seen it and I have read about it, but off the top of my head I cannot remember which book it is in. Ther may be a reference for it at: http://apple2history.org/ so you might start there.
Good Hunting. Smile

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Steven (gsmcten)

"Apple ][.....It's ALIVE!!!!!"

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Joined: Jul 6 2009
Posts: 44
Re: Colour bleed?

gsmcten wrote:

"Color Killer"

Many moons ago (between '78 and '80), Woz was having that same problem with color bleed.
As I remember the story, he came up with the "Color Killer" hack and placed the procedure into one of the books that came out during that time period.
I have seen it and I have read about it, but off the top of my head I cannot remember which book it is in. Ther may be a reference for it at: http://apple2history.org/ so you might start there.
Good Hunting. Smile

http://www.applefritter.com/node/6915 :

Quote:

Docupack Volume 1
The Woz Pack II and Other Assorted Goodies
Apple Pugetsound Program Library Exchange
138 pages
A Collection of Apple II Documentation. Furnished Through Courtesy of Apple Computer Inc. Assembled and Distributed by Apple Puget Sound Program Library Exchange

Amoung the interesting information are ads from the late 70s.
Table of Contents:
TED II+
Line Number Fross Reference
Symbol Cross Reference
Renumber/Append
Pack & Load
Machine Code Relocation Notes
Tape Verify
High Resolution Graphics Subroutines
Shape Generator
SWEET 16 Introduction
SWEET 16 The 6502 Dream Machine
Lazarus
Floating Point Routines
Auto Repeat for Monitor Commands
Integer Basic Subroutine Calls
STAR TREK
HI-RES Color Modification
Color Killer Modification

http://www.applefritter.com/files/Call-APPLE%20Woz%20Pak%202%201979.pdf

mmphosis's picture
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Joined: Aug 18 2005
Posts: 314
Re: Colour bleed?

That's not a bug. It's a feature!

Check out the images from this version of AppleWin: http://wsxyz.net/applewin.html

You could adjust your monitor/TV to reduce the amount of color. On old TVs this adjustment knob was usually called "COLOR." I think that there was also a color trim pot on the motherboard of the Apple II plus.

http://www.applefritter.com/content/apple-ii-color-trim

I've also fed the video of the Apple II from the other video out on the motherboard and I think that the power is roughly double that of the regular video out which really saturated the display.

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Joined: Jul 30 2011
Posts: 86
Re: Colour bleed?

Excellent information Guys, Thanks very much.

...........and yes, I suppose it is a feature!